Transitioning multi-core fiber to plural single core fibers

ABSTRACT

A method and system connects multiple cores within one fiber, e.g., a multi-core fiber (MCF), to multiple fibers with single-cores. The single-core fibers can then be terminated by traditional envelopes, such as a single core LC envelope. A connector holds the single-core fibers into a pattern that matches a pattern of all, or a sub group, of the individual cores of the MCF. The single-core fibers may all be terminated to individual connectors to form a fanout or breakout cable. Alternatively, the single-core fibers may extend to another connector wherein the single-core fibers are regrouped into a pattern to mate with the cores of another MCF, hence forming a jumper. One or more of the single core fibers may be terminated along the length of the jumper to form a jumper with one or more tap accesses.

This application is a continuation of U.S. application Ser. No.16/004,388 filed Jun. 9, 2018, which is a continuation of U.S.application Ser. No. 15/248,264 filed Aug. 26, 2016, now U.S. Pat. No.9,995,885 granted Jun. 12, 2018, which is a continuation of U.S.application Ser. No. 14/170,781 filed Feb. 3, 2014, now U.S. Pat. No.9,429,721 granted Aug. 30, 2016, which claims the benefit of U.S.Provisional Application No. 61/759,547, filed Feb. 1, 2013. The contentsof each application are herein incorporated by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to fiber optic cordage useful as a fanout,a partial fanout, such as a jumper with one or more taps, or a jumper toreorder cores of a multi-core fiber (MCF). More particularly, thepresent invention relates a connector for such cordage, wherein theconnector has several single core fibers arranged within a single holderof a ferrule, so as to mate with all, or several, cores of a MCF of amating connector, such that the MCF is broken out into single corefibers, which can be more easily and conventionally manipulated.

2. Description of the Related Art

Optical network operators are continuing to look for ways to obtainincreased density of optical fiber networks. One method for packaginghigher numbers of light carrying paths in a small space is through theuse of a MCF. A MCF typically comprises a central core surrounded byseveral satellite cores in a radial pattern surrounding the centralcore. Each of the central and satellite cores is potentially a lightcarrying path, and the MCF thus provides multiple parallel paths foroptical signal transmission and/or reception in a single fiber.

A MCF is known in the existing arts. See for example, U.S. Pat. Nos.5,734,773 and 6,154,594 and U.S. Published Applications 2011/0229085,2011/0229086 and 2011/0274398, each of which is herein incorporated byreference. In the background art of U.S. Published Application2011/0274398, as depicted in FIGS. 1 and 2, a MCF 180 has a central core181 and multiple satellite cores 182, e.g., six satellite cores 182-1,182-2, 182-3, 182-4, 182-5 and 182-6, in a common cladding layer 184.The satellite cores 182 are positioned around the central core 181symmetrically, at the vertices of a regular hexagon 183.

Each of the central and satellite cores 181 and 182 exhibits a samediameter. The central core 181 and each of the satellite cores 182 has adiameter of about 26 micrometers (um), depicted as distance A in FIG. 2.A center to center spacing between adjacent central and satellite cores181 and 182 is about 39 um, depicted as distance B in FIG. 2. Otherdimensions and spacing, besides those shown in U.S. PublishedApplication 2011/0274398, as depicted in FIGS. 1 and 2, are known in thebackground art. Also, more or fewer satellite cores 182 are known in thebackground art. Each of the central and satellite cores 181 and 182 maycarry a unique light signal. Each MCF 180 is affixed within a ferruleand terminates at or near an end surface 245 of the ferrule. The ferrulemay be part of a connector, which facilitates communicating the signalsof the central and satellite cores 181 and 182 to a device via a port,or to further cabling via an adapter.

FIG. 3 depicts a typical connector 201 having a cylindrical ferrule 203with a holder, e.g., a cylindrical central bore, presenting an end of asingle MCF 180 for mating to another connector, via an adapter, or forcommunicating with a port of a device. FIG. 3A is a perspective viewshowing a ferrule assembly 232 within the connector 201, which extendsalong an axis 236. The ferrule assembly 232 includes the ferrule 203, aferrule barrel 241 and tubing 242. The ferrule 203 has its holder formedas a precision hole extending down its length, along axis 236. The holeis shaped to closely receive a bare MCF 180 from a stripped end of anoptical fiber cable 244. The bare MCF 180 is cleaved at the ferrule'send surface 245 and polished, resulting in an exposed fiber end face, asdepicted in FIG. 2. Ferrule barrel 241 includes a hexagonal flange 246and a front cone portion 249 having a pair of slots 247 in itsperimeter. The structures of FIG. 3A are conventional and can be seen inUS Patent Application Publication 2011/0229085.

FIG. 4 depicts an MT-type ferrule 303 having first and second holes 305and 307 for accepting alignment pins of a mating ferrule. Between thefirst and second holes 305 and 307, the MT-type ferrule 303 presents anarray of twelve fiber ends of MCFs 180-1 through 180-12 forcommunicating to MCFs of the mating ferrule. The fiber ends are locatedwithin holders, e.g., cylindrical channels, of the ferrule 303. Anaccess window 309 opens to the MCFs 180-1 through 180-12 and can be usedto flood epoxy into the v-grooves below the window 309 and/or thecylindrical channels, as is conventional in the art. US PatentApplication Publication 2004/0189321, which is herein incorporated byreference, shows a typical MT ferrule.

Although FIG. 3 shows an LC type connector 201 and FIG. 4 shows a MTferrule 303, which could be used in a MPO/MTP type connector, otherconnector styles for presenting a single MCF or multiple MCFs in anordered array are known in the existing art, such as ST, SC and MT-RJ.Further the row of MCFs presented by the ferrule 303 may include more orfewer MCFs, such as eight or sixteen MCFs in one or two or more rows.Hereinafter, the term holder is broad enough to encompass all structuresholding a fiber, such as v-grooves and channels with circular or othernon-circular cross sectional shapes.

Fiber optic jumpers, patch cords, trunk cables, fanouts and other cableconfigurations provide optical connectivity in numerous spaces includinglocal area networks (LANs), wide area networks (WANs), datacenters,vehicles, aircraft and ships. Historically, fanouts and jumpers haveused one or more single-core optical fibers to mate with one or moresingle-core optical fibers presented by a termination. With the adventof the MCF, new fanouts and new jumpers are needed to deal with themultiple cores within a MCF.

SUMMARY OF THE INVENTION

The Applicant has appreciated that some applications, i.e. patching,link testing, link monitoring, cross connects, etc. require the opticalcores of a MCF to be separated and routed to different terminationpoints. It would be desirable to provide an easy and effective way ofrouting one or more individual cores of a MCF to different locations.

It is an object of the present invention to address one or more of theneeds in the prior art, as appreciated by the Applicant.

The Applicant has appreciated that it would be beneficial to providefanout cordage or jumper cordage with one or more taps, which can matewith one or more MCFs presented by a ferrule, wherein the cordage isconstructed of single-core fibers, such that terminations at the remoteend of the fanout cordage, or at the intermediate tap or taps along thejumper cordage, can be made using conventional single core connectors.The Applicant has also appreciated that a jumper with single-core fiberscan be used to reorder cores of a MCF from a first end of the jumper toa second end of the jumper. The reordering of the cores may facilitatevarious connection methods, daisy-chaining patch cords between devices,and/or data security.

These and other objectives are accomplished by a method and system forconnecting multiple cores within one fiber, e.g., a MCF, to multiplefibers with single-cores. The single-core fibers can then be terminatedby traditional envelopes, such as a typical single core LC typeenvelope, as depicted in FIG. 3. The invention provides a connectorholding the single-core fibers into a pattern that matches a pattern ofall, or a sub group, of the individual cores of the MCF. The single-corefibers may all be terminated to individual connectors to form a fanoutor breakout cable. Alternatively, the single-core fibers may extend toanother connector wherein the single-core fibers are regrouped into apattern to mate with the cores of another MCF, hence forming a jumper.One or more of the single core fibers may be terminated along the lengthof the jumper to form a jumper with one or more tap accesses.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus, are not limits ofthe present invention, and wherein:

FIG. 1 is an end view of a multi-core optical fiber, in accordance withthe prior art;

FIG. 2 is an end view of the multi-core optical fiber of FIG. 1, showingthe dimensions and spacings of the cores, in accordance with the priorart;

FIG. 3 is a perspective view of an LC fiber optic connector, inaccordance with the prior art;

FIG. 3A is a perspective view of a ferrule assembly within the LC fiberoptic connector of FIG. 3;

FIG. 4 is a perspective view of an MT ferrule for use in an MTP/MPOfiber optic connector, in accordance with the prior art;

FIG. 5 is a cross sectional view showing a fanout from a ferruleassembly, in accordance with a first embodiment of the presentinvention;

FIG. 6 is a close-up view of an end surface of the ferrule assembly,taken along line VI-VI in FIGS. 5 and 8;

FIG. 7 is an end view of a ferrule, in accordance with a secondembodiment of the present invention;

FIG. 8 is a cross sectional view taken along line VIII-VIII in FIG. 7;

FIG. 9 is a cross sectional view illustrating a jumper made withmultiple single core fibers with tap access to one of the single corefibers;

FIG. 10 is a cross sectional view illustrating a jumper made withmultiple single core fibers with tap access to two of the single corefiber;

FIG. 11 is a cross sectional view illustrating a jumper made withmultiple single core fibers with tap access in two locations for one ofthe single core fibers;

FIG. 12 is a perspective view showing an MT type ferrule with a holderhaving a cross sectional shape to assist in gathering of single-corefibers into a pattern suitable to mate with a MCF;

FIG. 13 is a top view of the ferrule of FIG. 12;

FIG. 14 is a side view of the ferrule of FIG. 12;

FIG. 15 is an end view of the ferrule of FIG. 12;

FIG. 16 is a close-up view of one of the holders in FIG. 15;

FIG. 17 is an end view of a ferrule holding three single-core fibersdimensioned to mate with a subset of cores within the MCF of FIGS. 1-2;

FIG. 18 is a diagram illustrating the overlapping of cores between thearrangement of FIG. 17 and the arrangement of FIG. 1;

FIG. 19 is an end view of an alternate multi-core optical fiber havingeight satellite cores surrounding a larger central core;

FIG. 20 is an end view of a ferrule holding four single-core fibersdimensioned to mate with a subset of cores within the MCF of FIG. 19;and

FIG. 21 is a diagram illustrating the overlapping of cores between thearrangement of FIG. 19 and the arrangement of FIG. 20.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention now is described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art.

Like numbers refer to like elements throughout. In the figures, thethickness of certain lines, layers, components, elements or features maybe exaggerated for clarity. Broken lines illustrate optional features oroperations unless specified otherwise.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention.Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the specification andrelevant art and should not be interpreted in an idealized or overlyformal sense unless expressly so defined herein. Well-known functions orconstructions may not be described in detail for brevity and/or clarity.

As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items. As used herein, phrases such as “between X and Y” and“between about X and Y” should be interpreted to include X and Y. Asused herein, phrases such as “between about X and Y” mean “between aboutX and about Y.” As used herein, phrases such as “from about X to Y” mean“from about X to about Y.”

It will be understood that when an element is referred to as being “on”,“attached” to, “connected” to, “coupled” with, “contacting”, etc.,another element, it can be directly on, attached to, connected to,coupled with or contacting the other element or intervening elements mayalso be present. In contrast, when an element is referred to as being,for example, “directly on”, “directly attached” to, “directly connected”to, “directly coupled” with or “directly contacting” another element,there are no intervening elements present. It will also be appreciatedby those of skill in the art that references to a structure or featurethat is disposed “adjacent” another feature may have portions thatoverlap or underlie the adjacent feature.

Spatially relative terms, such as “under”, “below”, “lower”, “over”,“upper”, “lateral”, “left”, “right” and the like, may be used herein forease of description to describe one element or feature's relationship toanother element(s) or feature(s) as illustrated in the figures. It willbe understood that the spatially relative terms are intended toencompass different orientations of the device in use or operation inaddition to the orientation depicted in the figures. For example, if thedevice in the figures is inverted, elements described as “under” or“beneath” other elements or features would then be oriented “over” theother elements or features. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the descriptors ofrelative spatial relationships used herein interpreted accordingly.

The invention described herein guides light from multiple cores withinone fiber, e.g., a MCF, to multiple fibers, each with a single-core. Thesingle-core fibers can then be terminated by traditional methods. Theinventive device, a first example of which is illustrated in FIGS. 5-6,groups multiple single-core fibers into a pattern that matches a patternof individual cores of the MCF.

FIGS. 5-6 show a connector system, in accordance with a first embodimentof the present invention. A ferrule 103 has an end surface 102. A holder104 is formed in the ferrule 103 and extends from a first or entranceend 105 of the ferrule 103 up to a second end of the ferrule 103,presenting the end surface 102.

A plurality of single-core optical fibers 106, such as seven single-corefibers 106-1, 106-2, 106-3, 106-4, 106-5, 106-6 and 106-7, are mountedin the holder 104 with first ends of the plurality of single-coreoptical fibers 106 arranged in a given pattern at the end surface 102 ofthe ferrule 103. The given pattern is best seen in the end view of FIG.6.

FIG. 6 shows the ferrule 103 holding six single-core fibers 106-1,106-2, 106-3, 106-5, 106-6 and 106-7 equally spaced around a seventhsingle-core fiber 106-4. All the single-core fibers 106 having the samecore (CO) diameter and the same cladding (CL) diameter. The core CO(center circle in each single-core fiber 106) has a diameter A, which issized to closely match each core diameter A in the conventional MCF 180depicted in FIG. 2, e.g., about 26 um. The cladding CL (outer ringencircling the core in each single-core fiber 106) has a diameter B,which is about 39 um. The dimension B of the cladding CL creates offsetdistances equal to distance B between the centers of the cores CO, whichmatch the offset distances B in the MCF 180 of FIG. 2, such thatefficient unidirectional or bidirectional transmission can occur betweenthe seven single-core fibers 106-1 through 106-7 and the cores 181 and182-1 through 182-6 of the MCF 180, when the fiber ends are aligned andmated within an adapter.

The single-core fibers 106 are held in place by epoxy 107. The epoxy 107is cured thermally or anaerobically, by UV light or other means. Theferrule 103 may be held by a ferrule barrel 241 having flanges 246, in asame or similar manner as the ferrule 203 is held in the prior art ofFIG. 3A. The rear of the ferrule barrel 241 may include a collar 108with a retaining ridge 109 to hold the tube 242 of FIG. 3A. The ferrule103 and ferrule barrel 241 may be added to the connector envelope, asdepicted in FIG. 3, to form an LC connector.

FIG. 5 depicts an individual fiber connector 110-1 through 110-7attached to a second end of each of the plurality of single-core opticalfibers 106-1 through 106-7, respectively. A length of each single-coreoptical fiber 106-1 through 106-7 between the ferrule 103 and theindividual fiber connectors 110-1 through 110-7 includes a polymercoating and/or a jacket. After, or as, the single-core optical fibers106-1 through 106-7 enter the ferrule barrel 241, any jacket is removed,leaving only the core, cladding and potentially an acrylate coating.Before, or as, the single-core optical fibers 106-1 through 106-7 enterthe holder 104 within the ferrule 103, the acrylate layer is removed.This leaves only the core CO and cladding CL on each single-core opticalfiber 106-1 through 106-7, such that the cladding CL layers abut eachother, as shown in FIG. 6. Although the acrylate layers have beendescribed as being removed from the single-core fibers 106 at portionswithin the ferrule 103, the bare acrylate layers may extend through theferrule 103 to the terminations at the end surface 102 in someapplications, if desired.

The given pattern, as depicted in FIG. 6, includes a central single-coreoptical fiber 106-4 surrounded by six satellite single-core opticalfibers 106-1, 106-2, 106-3, 106-5, 106-6 and 106-7 in a hexagonalpattern. The given pattern was selected so as to mate with the patternof the cores 181 and 182 of the MCF 180 in FIGS. 1 and 2. Of course, ifthe pattern of the cores in the MCF 180 were different, the pattern ofthe single-core fibers 106 in the holder 104 of the ferrule 103 would bemodified to mirror the different core pattern of the MCF 180, as will befurther explained hereinafter.

In the first embodiment of the invention, the ferrule 103 is acylindrical member and the holder 104 is located along a central axis,e.g., axis 236 in FIG. 3A, of the ferrule 103. The holder 104 extendsfrom a first end 105 of the ferrule 103 to a second end of the ferrule103, with the second end of the ferrule 103 including the end surface102. The ferrule 103 is suited for use in a connector envelope, like theLC connector depicted in FIG. 3.

In a second embodiment of the present invention, as depicted in FIGS.7-8, an MT type ferrule 112 is employed. The MT type ferrule 112 may beformed in a same or similar manner as the MT ferrule 303 of FIG. 4. AnMT ferrule 112 is but one example of a ferrule having a rectangularcross section. A first holder 111-1 extends from a first end 113 of theferrule 112 to a second end 114 of the ferrule 112, with the second end114 of the ferrule 112 including the end surface 102 (see the close-upview of FIG. 6). A second holder 111-2 is formed in the ferrule 112,parallel to the first holder 111-1 and extends from the first end 113 tothe second end 114. In particular, FIG. 7 depicts twelve parallel andequally spaced holders 111-1 through 111-12 within the ferrule 112. Ofcourse more or fewer holders 111 may be employed, such as eight holders,and one, two or more rows of holders 111 may be employed. Further, it isnot required that the holders 111 be equally spaced or parallel.

FIG. 8 is a cross sectional view taken along line VIII-VIII in FIG. 7.In FIG. 8, epoxy 107 has been flooded into the window 309 to secure thesingle-core optical fibers 106-1 through 106-7 into V-grooves 115 (alsosee FIG. 13) and the holders 111-1 through 111-12, e.g., circularchannels. In the same manner as described above in conjunction with FIG.5, the single-core optical fibers 106-1 through 106-7 are fanned out toindividual connectors 110-1 through 110-7, respectively. Although FIGS.5 and 8 have illustrated cylindrical ferrules for the end terminations110 of the single-core fibers 106, the distal ends of the multiplesingle-core fibers 106 can be terminated by various traditional methodsincluding but not limited to fusion splice, mechanical splice,multifiber array connectors or any type of single fiber connectors.

Next, with reference to FIGS. 9-11, a jumper aspect of the presentinvention will be described. In FIG. 9, first and second MCFs 121 and122, each include a plurality of cores 181 and 182 arranged inrespective patterns. One core of the first MCF 121, e.g., core 182-6,and one core of the second MCF 122, e.g., core 182-6, can be considereda “target” core.

A first connector includes a first ferrule assembly 123 terminating afirst end of the first MCF 121 and presenting the plurality of cores 181and 182 of the first MCF 121 in a first pattern, e.g., the pattern ofFIG. 2. A second connector includes a second ferrule assembly 124terminating a first end of the second MCF 122 and presenting theplurality of cores 181 and 182 of the second multi-core fiber 122 in asecond pattern, e.g., the mirror image of FIG. 2.

A multiple fiber segment 125 has a third connector with a third ferruleassembly 126 terminating first ends 127 of the multiple fiber segment125 and a fourth connector with a fourth ferrule assembly 128terminating second ends 129 of the multifiber segment 125. The thirdferrule assembly 126 is connectable to the first ferrule assembly 123,e.g., by a first adapter sleeve 130 of a first adapter, which brings theend surfaces of the first and third ferrule assemblies 123 and 126 intoabutment. The fourth ferrule assembly 128 is connectable to the secondferrule assembly 124, e.g., by a second adapter sleeve 131 of a secondadapter, which brings the end surfaces of the second and fourth ferruleassemblies 124 and 128 into abutment.

Single-core fibers 106-1 through 106-6 of the multiple fiber segment 125have their first ends 127 residing within the holder 104 of the thirdferrule assembly 126 and arranged in a pattern to align with cores 181and 182-1 through 182-5 of the first MCF 121 in the first ferruleassembly 123, when the first and third ferrule assemblies 123 and 126are mated. The single-core fibers 106-1 through 106-6 of the multiplefiber segment 125 have their second ends 129 residing within the holder104 of the fourth ferrule assembly 128 and arranged in a pattern toalign with cores 181 and 182-1 through 182-5 of the second MCF 122 inthe second ferrule assembly 124, when the fourth and second ferruleassemblies 128 and 124 are mated.

The multiple fiber segment 125 has a first target fiber, e.g.,single-core fiber 106-7, extending from the third ferrule assembly 126to a first jumper ferrule 132 of a first jumper connector (not shown)located at a free, second end 133 of the first target fiber, e.g.,single-core fiber 106-7. A termination, first end 127 of the firsttarget fiber 106-7 within the third ferrule assembly 126 is aligned witha termination end of the target core 182-6 of the first MCF 121 withinthe first ferrule assembly 123, when the first and third ferruleassemblies 123 and 126 are mated. A second target fiber, e.g.,single-core fiber 106-7′, extends from the fourth ferrule assembly 128to a second jumper ferrule 134 of a second jumper connector (not shown)located at a free end 135 of said second target fiber, e.g., single corefiber 106-7′. A termination end 129 of the second target fiber 106-7′within the fourth ferrule assembly 128 is aligned with a termination endof the target core 182-6 of the second MCF 122 within said secondferrule assembly 124, when the fourth and second ferrule assemblies 128and 124 are mated.

FIG. 10 illustrates that jumper cordage, in accordance with the presentinvention, may include taps for more than one single-core fiber in themultiple fiber segment 125. For example, in addition to forming a tap onsingle-core fiber 106-7, 106-7′ using first and second jumper ferrules132 and 134, it is possible to also introduce a tap in single-core fiber106-1, 106-1′ using third and fourth jumper ferrules 137 and 138.

FIG. 11 illustrates that the jumper cordage, in accordance with thepresent invention, may include several taps along a same single-corefiber 106-7, 106-7′ and 106-7″ within the multiple fiber segment 125.For example, single-core fiber 106-7, 106-7′ and 106-7″ may have a firstjumper formed at first and second jumper ferrules 132 and 134 and asecond jumper formed at fifth and sixth jumper ferrules 139 and 140.

Although FIGS. 9-11 have illustrated three variations of jumper cordagewith taps, it should be appreciated that many variations are possible,whereby more than two single-core fibers 106 could be tapped and morethan two taps could be inserted along one single-core fiber 106. Inprincipal, one or more single-core fibers 106 of the plurality of singlecore fibers 106 may be terminated while the remaining single core fibers106 connect first and second MCFs 121 and 122. Placing a multiple fiberjumper between two multi-core fibers 121 and 122, cutting one of thesingle-core fibers 106 and terminating each free end of the cut ortarget fiber 106 allows signals on that terminated target fiber 106 tobe used in the middle of a length of the multiple fiber jumper withoutthe need to individually terminate every one of the single-core fibers106 of the jumper at the usage point. In a security system, for example,having a number of sensors that need to communicate with a base station,each sensor could communicate over a different individual fiber, whichfiber could connect to its particular sensor at different physicallocations along the jumper, using the arrangements of FIGS. 9-11.

FIGS. 12-16 illustrate an embodiment wherein the walls forming theholder create an alignment structure to assist in forming thesingle-core fibers 106 into the desired pattern, e.g., FIG. 6, to matchthe pattern of optical cores 181, 182 in the MCF 180 to which theferrule is connectable. In the case of the pattern of FIGS. 1 and 2, acircular holder 104, as shown in FIG. 6 works well. However, for otherpatterns, a differently shaped holder can offer advantages.

FIG. 12 is a perspective view showing an MT ferrule 143 with holders141-1 through 141-12 extending to a mating face or end surface 145.FIGS. 13 and 14 are top and side views, respectively, of the ferrule143. The MT ferrule 143 is the same or similar to the MT ferrule of FIG.4, except for the cross sectional shape of the holders 141-1 through141-12.

FIG. 15 is an end view of the MT ferrule 143 showing the end surface145. The first holder 141-1 is populated with four single-core fibers147-1, 147-2, 147-3 and 147-4, the remaining holders 141-2 through141-12 are empty in FIGS. 12-15, but may be populated with pluralsingle-core fibers or a MCF, as desired in the end use.

FIG. 16 is a close-up view the first holder 141-1. The square crosssectional shape of the first holder 141-1 assists in the gathering ofthe single-core fibers 147-1, 147-2, 147-3 and 147-4 into a desiredpattern. In the depicted embodiment, the desired pattern would besuitable to mate with a MCF having four cores in the same ordering. Ofcourse, other alignment features of the holders could create other crosssectional shapes besides a square cross sectional shape. In general, thecross sectional shape may be formed by one or more intersecting edgesdefining a border of the holder, wherein the cross section of the holderis taken perpendicular to the direction in which the holder extends. Anysuch cross sectional shape with one or more intersecting side edgescould be used to assist in assembling the single-core fibers into adesired pattern, such as a D-shaped cross sectional shape or atriangular-shaped cross sectional shape.

In the embodiments, presented above, the single-core fibers 106 or 147presented by the holders 104, 111, 141 were equal in number to thenumber of cores 181 and 182 presented by the MCF 180. However, theteachings of the present invention may be applied to a situation whereinthe number of single core fibers 106 or 147 may be fewer in number thanthe cores 181 and 182 of the MCF 180, as will be described below.

FIG. 17 is an end view of a holder 104 within a ferrule 151. FIG. 17 issimilar to the view of FIG. 6, however in FIG. 17, the holder 104presents the ends of three single-core fibers 153-1, 153-2 and 153-3 atthe end surface 102′ of the ferrule 151. The diameter of the core CO ofeach single-core fiber 153-1, 153-2 and 153-3 is the same as thediameter of the cores CO of the single-core fibers 106 in FIG. 6 and thesame as the diameter of the cores 181 and 182 of MCF 180 in FIG. 2,i.e., dimension A or about 26 um. The cladding CL of each single-corefiber 153-1, 153-2 and 153-3 is much thicker and presents a largerdiameter than the cladding CL of the single-core fibers 106 in FIG. 6.The cladding CL creates an offset distance B from the center of theholder 104 to the centers of the cores CO of each single-core fiber 153,i.e., equal to the offset B depicted in FIGS. 2 and 6.

The oversized cladding CL of each single-core fiber 153 creates anoffset between the cores CO of the single-core fibers 153, such thatwhen the end surface 102′ of ferrule 151 is abutted to the end surface245 of a ferrule holding MCF 180, e.g., during connector mating via anadapter, the three cores CO of the single-core fibers 153, as presentedat the end surface 102′ will align with three satellite cores 182 of theMCF 180. More particularly, as shown in the diagram of FIG. 18, the coreCO of single-core fiber 153-1 aligns to the core 182-2 of MCF 180, thecore CO of single-core fiber 153-2 aligns to the core 182-4 of MCF 180,and the core CO of single-core fiber 153-3 aligns to the core 182-6 ofMCF 180. The termination of FIG. 17 is useful as a fanout or breakout ofa MCF 180, wherein only satellite cores 182-2, 182-4 and 182-6 arebright, e.g., used in the MCF 180, or are needed by a particular pieceof equipment connected downstream of the termination of the MCF 180.

FIG. 18 demonstrates a general concept in accordance with the presentinvention that one may couple a MCF containing n cores to a greaternumber or a fewer number of single-core fibers by selecting individualfibers with smaller or larger cladding and a geometric relationship thataligns the fiber cores. For example, an MCF 180 made with seven 26micron diameter cores, six equally spaced around one on a radius of 39microns, e.g., FIG. 2, could be mated to three individual fibers each of67.55 micron nominal cladding diameter with 26 micron diameter singlecores, e.g., FIG. 17. The group of three separate fibers 153-1, 153-2and 153-3 is bonded into a single holder 104, e.g., a through hole orgroove, in a single fiber or a multi-fiber connector ferrule 151. Theholder 104 in the ferrule 151 may have a circular cross section, atriangular cross section, or other cross sectional geometry thataccurately positions the fiber.

FIG. 19 illustrates an alternative design for a MCF 161. The MCF 161includes a central core 163 and eight satellite cores 165-1 through165-8. Each satellite core 165-X is spaced from a center of the centralcore 163 by a same distance X. Further, each satellite core 165 isequally spaced from each other along a radius line (indicated by adashed line in FIG. 19) located at distance X from the center of thecentral core 163. Other than the sizing and spacing, the MCF 161 may beidentical in structure, function, and material as the MCF 180 describedabove.

FIG. 20 is an end view of a holder 104 within a ferrule 169. FIG. 20 issimilar to the view of FIG. 6, however in FIG. 20, the holder 104presents the ends of four single-core fibers 171-1, 171-2, 171-3 and171-4 at the end surface 102″ of the ferrule 169. A diameter of the coreCO of each single-core fiber 171-1, 171-2, 171-3 and 171-4 is the sameas the diameter of the satellite cores 165 of the MCF 161. A diameter Zof the cladding CL of the single-core fibers 171 creates an offsetdistance X from the center of the holder 104 to the centers of the coresCO of each single-core fiber 171, i.e., equal to the offset X depictedin FIG. 19.

The oversized cladding CL of each single-core fiber 171 creates anoffset between the cores CO of the single-core fibers 171, such thatwhen the end surface 102″ of ferrule 169 is abutted to the end surfaceof a ferrule holding MCF 161 (FIG. 19), e.g., during connector matingvia an adapter, the four cores CO of the single-core fibers 171, aspresented at the end surface 102″, will align with four satellite cores165 of the MCF 161. More particularly, as shown in the diagram of FIG.21, the core CO of single-core fiber 171-1 aligns to the core 165-2 ofMCF 161, the core CO of single-core fiber 171-2 aligns to the core 165-4of MCF 161, the core CO of single-core fiber 171-3 aligns to the core165-6 of MCF 161, and the core CO of single-core fiber 171-4 aligns tothe core 165-8 of MCF 161. The termination of FIG. 20 is useful as afanout or breakout of a MCF 161, wherein only satellite cores 165-2,165-4, 165-6 and 165-8 are bright, e.g., used in the MCF 161, or areneeded by a particular piece of equipment connected downstream of thetermination of the MCF 161.

FIG. 21 demonstrates how four single-core fibers 171 with 33 microndiameter cores and 82.45 micron diameter cladding, e.g., distance Z,equally spaced on a 58.3 micron radius, e.g., distance X, can couple tofour cores 165-2, 165-4, 165-6 and 165-8 of a nine core MCF 161 wherethe eight satellite cores 165 measure 33 microns in diameter and areequally spaced on a 58.3 micron radius. The group of four separatefibers 171 is bonded into a single holder 104, e.g., through hole orgroove, in a single fiber or a multi-fiber connector ferrule 169. Theholder 104 of the ferrule 169 may have a circular cross section, asquare cross section (like FIGS. 12, 15 and 16) or other cross sectionalgeometry that accurately positions the single-core fibers 171.

The connector system as described above including a fanout or a jumperwith or without taps may be produced by a method including providing aferrule having an end surface, a holder formed in the ferrule andextending up to the end surface, and a plurality of single-core opticalfibers. Inserting the plurality of single-core optical fibers into theholder with first ends of the single-core fibers residing approximatelyat, or extending out from the end surface of the ferrule. To facilitatethe insertion step, an inner diameter of the holder in the ferrule maybe slightly larger, e.g., approximately one micron larger, than thecollective diameter of the group single-core fibers. For example, in asix around one configuration (FIG. 6), the collective diameter of thesix-around-one configuration is equal to three times a center claddingdiameter or three times a satellite cladding diameter.

Arranging the first ends of the plurality of single-core fibers into adesired ordering relative to the ferrule. The fibers can be rotated andclocked within the ferrule to a keying feature on the ferrule, ferrulebarrel or connector housing. The arranging is performed prior to anyepoxy curing and creates the desired pattern to allow for directconnection or cross connection at the ferrule end surface. The fibersmay also be clocked and cured randomly in the ferrule, and then theferrule is later oriented in a connector, so as to clock the ferrule toclocking features of the connector. The pattern of the single-corefibers can be mirror images, as viewed at the end surfaces of ferruleassemblies 126 and 128 in FIG. 9 or may be the same patterns, i.e., notmirror images. Hence, it is possible to reorder the single-core fibersin the satellite positions along the length of the jumper cable, whichmay prove useful to provide correct routing of signals betweentransmitters and receivers within single cords or when concatenatingcords and/or cables. The reordering of single-core fibers in satelliteand/or center positions could also be used as a keying function toprotect data, so that only a cord with properly re-routed single-corefibers would link the MCF 180 into a port of a device in a requiredordering to allow for communication between the device and the MCF 180.

Epoxy may be used in adhering the single-core fibers within the holder.The epoxy may be inserted into the ferrule before or after thesingle-core fibers, and capillary action will draw inviscid epoxythrough the longitudinal voids between the ferrule and single-corefibers. An epoxy with appropriate index of refraction may be used tocreate tunnels or capture light between fibers to reduce crosstalk. Therefractive index of the epoxy may be selected to either reduce orincrease cross-talk between the multiple fibers in the holder.Minimizing cross-talk is often desirable. However, under somecircumstances, it may be desirable to use one of the single-core fibersto eavesdrop on another single-core fiber. For example, the centersingle core fiber 106-4 in FIG. 6 can be used to eavesdrop on thesingle-core fibers in satellite positions. By selecting an epoxy havingan index of refraction that allows signals to leak from the centersingle-core fiber 106-4 to one of the satellite fibers, e.g., 106-1, thesatellite single-core fiber 106-1 can be monitored to reveal data on thecenter single-core fiber 106-4, or visa versa, in an unobtrusive manner.Hence, the present invention could be employed for example to provide atapping location for the center single-core fiber 106-4, while thecenter single-core fiber 106-4 and the remaining satellite single-corefibers 106-1 through 106-3 and 106-5 through 106-7 travel through thejumper to another connector where they connect to another MCF.

Finally, the method for forming a termination, in accordance with thepresent invention, includes cleaving and/or polishing the first ends ofthe plurality of single-core fibers. The Cleaving and/or polishing maybe performed at the end surface of the ferrule. The above steps createthe termination (FIG. 6) in a holder of a ferrule to mate with a firstMCF. If a fanout is to be produced, connectors or ferrules are installedat each second end of the plurality of single-core fibers 106, e.g. asdepicted in FIGS. 5 and 8. If a jumper is to be produced, second ends ofseveral of, or all of, the plurality of single-core fibers 106 areinstalled into a second holder of a second ferrule, e.g. as depicted inFIGS. 9-11.

Although the depicted embodiments have shown a single cladding layersurrounding the single-core fibers and a single cladding layer surroundthe MCF, some MCF and single core fibers may include a secondary outercladding. The principals and teachings of the invention still apply andthe dimensions and spacing can be adjusted to treat the secondarycladding as a simply a thicker single cladding layer. The inventiondefined herein also pertains to single and multi-core fibers withcladding diameters that may be constant over the length of the fiber ortaper larger or smaller over the length of the fiber.

The invention defined herein also applies to MCFs with cores arranged inrectangular arrays or non-symmetrically, or with combinations ofsingle-mode (SM) or multi-mode (MM) cores or with arrangements where oneor more of the “core” locations in the MCF is replaced by a smallermulti-core fiber. Although the MCF 180 has been illustrated with acircular outer perimeter, the MCF 180 can be made with a D shaped crosssection creating a flat that runs longitudinally along the MCF 180 for aportion or all of its length. The satellite single-core fibers 106-1through 106-3 and 106-5 through 106-7 can be clocked or orientedrelative to the flat of the MCF 180. The flat can align to a flat onD-shaped holder 104 or 111-1 in the ferrule 103 or 112 providing a meansof clocking the satellite single-core fibers 106-1 through 106-3 and106-5 through 106-7 relative to the ferrule 103 and 112 and relative tothe MCF 180. The connector housings have been omitted from the ferrulesin the figures depicting the present invention for the sake of clarity.

The present invention has been described above in terms of severalpreferred embodiments. However, modifications and additions to theseembodiments will become apparent to persons of ordinary skill in the artupon a reading of the foregoing disclosure. All such modifications andadditions comprise a part of the present invention to the extent theyfall within the scope of the several claims appended hereto.

We claim:
 1. A connector system comprising: a first ferrule having afirst end surface; a first holder formed in said first ferrule andformed as a single opening or groove extending up to said first endsurface; a plurality of single-core optical fibers mounted in said firstholder with first ends of said plurality of single-core optical fibersarranged in a first given pattern at said first end surface of saidfirst ferrule; a second ferrule having a second end surface; a secondholder formed in said second ferrule and formed as a single opening orgroove extending up to said second end surface; and a multi-core opticalfiber including a plurality of cores arranged in a second given pattern;said multi-core optical fiber being mounted in said second holder with afirst end of said multi-core optical fiber being located at said secondend surface of said second ferrule, wherein when said second ferrule ismated to said first ferrule, at least one of said plurality ofsingle-core optical fibers is aligned with at least one of said cores insaid multi-core optical fiber.
 2. The connector system of claim 1,wherein said plurality of single-core optical fibers are mounted in anabutting relationship along a length of said first holder.
 3. Theconnector system of claim 2, wherein each one of said plurality ofsingle-core optical fibers is aligned with a respective one of saidcores of said multi-core optical fiber.
 4. The connector system of claim2, wherein said first given pattern presents a number of single-corefiber ends which is less than a number of core ends presented by saidmulti-core fiber in said second given pattern.
 5. The connector systemof claim 2, wherein said first and/or second holder is formed as asingle opening or groove having a cross section configured to positionand/or angularly align said multi-core fiber and/or said first ends ofsaid plurality of single-core optical fibers.
 6. The connector system ofclaim 2, wherein said first holder is formed as a single opening orgroove having a cross section configured to position and/or angularlyalign said first ends of said plurality of single-core optical fibers.7. The connector system of claim 6, wherein the cross section includesone or more intersecting edges defining said first holder, and whereinthe cross section of said edges presents a square-shaped cross sectionor a D-shaped cross section or a triangular-shaped cross section.
 8. Aconnector system comprising: a first ferrule having a first end surface;a first holder formed in said first ferrule and formed as a singleopening or groove extending up to said first end surface; a plurality ofsingle-core optical fibers mounted in said first holder with first endsof said plurality of single-core optical fibers arranged in a firstgiven pattern at said first end surface of said first ferrule; anindividual fiber connector attached to a second end of a firstsingle-core fiber of said plurality of single-core optical fibers; asecond ferrule having a second end surface; and a second holder formedin said second ferrule and formed as a single opening or grooveextending up to said second end surface, wherein second ends of a secondand third single-core fiber of said plurality of single-core opticalfibers are mounted in said second holder and are arranged in a secondgiven pattern at said second end surface of said second ferrule.
 9. Theconnector system of claim 8, wherein said plurality of single-coreoptical fibers are mounted in an abutting relationship along a length ofsaid first holder.
 10. The connector system claim 9, wherein saidindividual fiber connector is a first individual fiber connector, andfurther comprising: a fourth single-core optical fiber; and a secondindividual fiber connector attached to a first end of said fourthsingle-core optical fiber, wherein a second end of said fourthsingle-core optical fiber is mounted in said second holder and is partof said second given pattern at said second end surface of said secondferrule.
 11. The connector system of claim 9, wherein said first givenpattern is selected to match a pattern of optical cores in a multi-corefiber to which said first ferrule is connectable.
 12. The connectorsystem of claim 9, wherein said first holder includes an alignmentstructure to assist in arranging said plurality of single-core opticalfibers in said first given pattern.
 13. The connector system of claim12, wherein said alignment structure includes one or more intersectingedges defining said first holder, as viewed in a cross section of saidfirst holder taken perpendicular to the direction in which said firstholder extends.
 14. The connector system of claim 9, wherein said firstferrule is a cylindrical member and said first holder is located along acentral axis of said first ferrule and extends from a first end of saidfirst ferrule to a second end of said first ferrule, with said secondend of said first ferrule including said first end surface.
 15. Theconnector system of claim 9, wherein cladding layers or acrylate layersof said plurality of single-core optical fibers abut each other at saidfirst end surface of said first ferrule.
 16. A connector systemcomprising: first and second multi-core optical fibers each including aplurality of cores arranged in a first pattern, one core of said firstmulti-core fiber and one core of said second multi-core fiber being atarget core; a first connector terminating a first end of said firstmulti-core optical fiber and presenting said plurality of cores of saidfirst multi-core fiber in a first pattern; a second connectorterminating a first end of said second multi-core optical fiber andpresenting said plurality of cores of said second multi-core fiber in asecond pattern; and a multiple fiber segment having a third connectorterminating first ends of said multiple fiber segment and a fourthconnector terminating second ends of said multifiber segment, said thirdconnector being connectable to said first connector and said fourthconnector being connectable to said second connector, at least one fiberof said multiple fiber segment having a first end residing within saidthird connector and aligned with one of said cores of said firstmulti-core optical fiber in said first connector, when said first andthird connectors are mated, said at least one fiber of said multiplefiber segment having a second end residing within said fourth connectorand aligned with one of said cores of said second multi-core fiber insaid second connector, when said fourth and second connectors are mated,wherein said multiple fiber segment has a first target fiber extendingfrom said third connector and a first jumper connector at a free end ofsaid first target fiber, a termination end of said first target fiberwithin said third connector being aligned with a termination end of saidtarget core of said first multi-core fiber within said first connectorwhen said first and third connectors are mated.
 17. The connector systemof claim 16, wherein said third connector is connectable to said firstconnector via a first adapter and said fourth connector is connectableto said second connector via a second adapter.
 18. The connector systemof claim 17, wherein said multiple fiber segment also has a secondtarget fiber extending from said fourth connector and a second jumperconnector at a free end of said second target fiber, a termination endof said second target fiber within said fourth connector being alignedwith a termination end of said target core of said second multi-corefiber within said second connector when said fourth and secondconnectors are mated.
 19. The connector system of claim 16, wherein saidmultiple fiber segment also has a second target fiber extending fromsaid fourth connector and a second jumper connector at a free end ofsaid second target fiber, a termination end of said second target fiberwithin said fourth connector being aligned with a termination end ofsaid target core of said second multi-core fiber within said secondconnector when said fourth and second connectors are mated, and whereinsaid multiple fiber segment also has a third target fiber extending fromsaid third connector and a third jumper connector at a free end of saidthird target fiber, a termination end of said third target fiber withinsaid third connector being aligned with a termination end of anothertarget core of said first multi-core fiber within said first connectorwhen said first and third connectors are mated.
 20. The connector systemof claim 19, wherein said multiple fiber segment also has a fourthtarget fiber extending from said fourth connector and a fourth jumperconnector at a free end of said fourth target fiber, a termination endof said fourth target fiber within said fourth connector being alignedwith a termination end of another target core of said second multi-corefiber within said second connector when said fourth and secondconnectors are mated.